Utilization of volatile fluxes in welding operations



Aug. 13, 1940. T. H. VAUGHN ET AL UTILIZATION OF VOLATILE FLUXES INWELDING OPERATIONS Filed Aug. 31, 1937 2 Sheets-Sheet l S M m m m THOMASH. VAUGHN ARTHUR R LVTLE ATTORNEY 2 SheetsSheet 2 km 1 .1 n I INVENTORSTHOMAS H. VAUGHN ARTHUR R. LVTLE ATTORNEY Aug. 13, 1 T. H. VAUGHN ET ALUTILIZATION OF VOLAI'ILE FLUXES IN WELDING OPERATIONS Filed Aug. 31,1937 Patented Aug. 13, 1940 UNITED STATES UTILIZATION OF VOLATILEFLUXESIN WELDING OPERATIONS Thomas H. Vaughn Niagara Falls, N. Y., bide andCarbon Research and Arthur R. Lytle, assignors to Union Car-Laboratories, Inc.,

, a corporation of New York Application August 31,

16 Claims.

The invention relates to welding, brazing and 5 utility in welding,brazing and soldering operations wherein a iiuxing agent is used whichis volatile under the conditions of its use.

Among the more important objects of the invention are to provide in awelding or similar operation for continuously introducing a uniformregulated amount of a volatile flux to the welding zone or to weldinggases flowing thereto; to provide in novel manner for preventingsubstantial deposition of solid hydrolysis products within a lineconducting a fuel gas and/or an oxygencontaining gas to a welding zoneor its equivalent; and to provide for continuously and uniformlyconducting to a welding zone a fuel gas mixture containing a selectedamount of a readily hydrolyzable volatile flux irrespective'of moisturepresent in the fuel gas.

Welding processes utilizing volatile fluxes such as the alkyl boratesalready are in use. In such processes, the fuel gas is bubbled through amixture of ethyl alcohol having an excess of boron oxide (B203). Theresultant ethyl borate picked up by the gas imparts a, decided fiuxingaction to the welding flame. Such processes have many disadvantagesinterfering with their full com-= mercial exploitation to the extentjustified by their apparent efiicacy. Thus the reaction pro= ducing theethyl borate simultaneously produces the insoluble boric acid which soonforms a thick slurry through which the welding gas cannot a pass. Toavoid this it is necessary to limit the concentrations of ethyl borateused to relatively small ones. Moreover, as the welding gas is bubbledthrough the ethyl alcohol-boric oxide mixture, the concentration ofethyl borate in both the mixture and the welding gas rapidly dimin ishesuntil eventually the amount of alcohol carried into the flame seriouslylowers the flame temperature, while the fiuxing action practicallyceases.

A. process for overcoming the objectionable features of the aforesaidprocesses and for insur ing the continuous addition of a welding gas oi.a uniform amount of a volatile flux is described in applicants copendingapplication for U. S. patent, Serial No. 56,042, filed December 24,1935, entitled Volatile welding fluxes. The present invention is incertain respects an improvement over the process of the said copendingapplication and facilitates the uniform and continuous feed to a weldingzone under a wide range of conditions of a gas containing any selectedamount of, a volatile flux, which amount may be regulated irrespectiveof the presence of moisture in the said gas at the source of supplythereof, or

1937, Serial No. 161,767 (Cl. 113-112) of the vapor pressure of the fluxunder the temperature conditions of its preparation and use.

The volatile or volatilizable flux utilized may be either a purecompound, a mixture of such compounds, or a solution of the same in avolatile liquid such as ethanol. In the latter instance an azeotropicsolution of the flux preferably is employed. in accordance with theinvention, a material improvement in welding, brazing and associatedoperations, both from the standpoint of economy in the use of the fluxand in the improved physi cal characteristics of the welded areas, areei-= iected by close and positive regulation at all times of the ratioof volatile flux to the fuel mixture flowing to the welding zone,independently of the percentage of the active flux in the flux fluid.This control prevents the use of wasteful amounts of volatile fiux andsolvent, with the resultant reduction in dance temperature.

Broadly considered, the invention involves the introduction into awelding zone, or into one or both of the welding gases flowing to awelding zone, of a volatile flux such as an alkyl borate or alkylsilicate volatilized from a body thereof maintained under selectedconditions of pressure and temperature. In certain modifications of theinvention the feed control of the flux may be facilitated by thetemperature control of the main body of flux or solution thereof, and/orby bypassing a regulated amount of one or both of the welding gaseseither through or over the surface of the said body of flux, thusregulating the partial pressure of the flux vapors in the fuel mixtureflowing to the welding zone.

In the accompanying drawings illustrating various forms of apparatusadapted forcarrying out the process features of the invention,

Figure i is a vertical section through one form oi flux chamber andassociated parts, parts being broken away;

Figure 2 is a vertical section through another form oi flux chamber;

Figure 3 shows in vertical section a modified form of flux chamber; a

Figure shows a blowpipe and still another type of associated fluxchamber, parts being shown in section;

Figure 5 is a somewhat diagrammatic view showing fuel gas and oxygenmanifolds, and

associated blowpipes and flux chamber, parts being shown in section; and

Figure 6 is a somewhat diagrammatic View of a modified apparatusassembly embodying the invention, parts being shown in section, andother. parts being broken away.

Referring to Figure 1, numeral ll designates a fluid-tight flux chamberadapted to hold a body of a volatilizable flux such as an alkyl borateor an alkyl silicate, or mixture thereof, as disclosed 2 in ouraforesaid copending application, in solution in a dry volatile solventtherefor, such as methanol and ethanol.

The chamber H has a removable fluid-tight closure l3, and a removablebottom I5 having a valve-controlled outlet l6; and it is provided with aheat-exchange jacket I! surrounding the walls, together withvalve-controlled inlet l9 and outlet 21 for passing a heat-exchangefluid through the said jacket.

For maintaining a uniform height of liquid fiux in chamber l I when thisis desired, there may be provided a flux storage vessel 23 having aclosure 25. A liquid conduit 21 having therein a float-controlled valve29 in vessel H, connects the vessels H and 23, and provides formaintaining a uniform liquid level in the former. A pressureequalizingline 3| also connects the two vessels.

For supplying a fuel gas such as acetylene to one or more blowpipes, afuel gas line 35 leads from a suitable source of supply, such as acylinder of acetylene or liquefied propane under high pressure, or alow-pressure acetylene generator. A branch line 3'! controlled by valve38 connects line 35 with the interior of vessel ll above the liquidlevel therein, and has an outlet end directed downwardly towards thesurface of the liquid. Vapor outlet lines 39, Q9, connect the upper endof container H with the inlet end of a fluid-tight filter chamber 4ihaving a removable closure Q3, and a plurality of layers 55 of mineralwool or other filtering medium maintained between retaining screens 36.Fuel gas line 35 also is connected with outlet line 50 by means of aconduit d1 controlled by valve Q9.

The outlet from the filter chamber is connected by means of conduit 5|with a fuel gas manifold 53 having spaced branch lines 55, 55,respectively connected with the valve-controlled fuel inlet lines 57 ofblowpipes T, each having an oxygen inlet line 59 controlled by a valve5!, and having a mixing chamber controlled bya valve t3. A flashbackarrester or trap, such as the trap 539 shown in Fig. 5, may be placed ineach line 55. The outlet end of the line 55 extends beneath the surfaceof a body of a suitable non-aqueous liquid in the trap. Such liquidpreferably should be substantially free from organic materials boilingaround 400 F. or below, inert to the flux compound. A light mineral oildistillate such as a crank case grade of hydrocarcarbon lubricating oilof lO-W viscosity functions very satisfactorily,

Figure 2 illustrates a modified form of flux vessel in which the fuelgas is introduced into the flux below the surface of the liquid. Thefiux chamber 15 is provided with a heat-exchange jacket 11 andassociated parts similar in construction to the chamber ll of Fig. 1.The fuel gas inlet line 'i 9 is connected with a valve-controlled branchline 89 which extends downwards to a point below the liquid level inchamber 15. A fluid outlet line 8| connects the upper part of chamber 15with the fuel gas line 19; and a valve 82 is in line 19 between lines 89and 8|. A flux inlet line 83 having a closure 84 is provided as shown.The chamber 15 has a removable bottom closure 85 and a valve-controlledflux drain line 86. A fiux storage chamber and associated parts similarto chamber 23 of Fig. 1 may be employed if desired,

In one modification of the process using the apparatus of Figs. 1 and 2,the regulated feed of the volatile flux is accomplished by controllingthe rate of vaporization of the fiux through temand should be chemicallyperature control of the liquid flux. In the modification shown in Fig.elements are so designed and regulated that the fuel gas passing throughthe vessel 15 is completely saturated with the flux mixture beforeleaving the vessel.

In the modification of the invention illustrated in Fig. 3, the flux ismaintained under a uniform positive pressure, and regulation is securedthrough a needle valve, the flux being sprayed or vaporized directlyinto the welding zone or into the fuel gas line leading to the blowpipeor manifold. This modification is use with fuel gas systems that areunder high pressures, such as those using high pressure dissolvedacetylene. The flux container 81 has a fluid-tight closure 88, avalve-controlled bottom outlet 89 for cleaning out the container, aheatexchange jacket 9|, a fuel gas inlet line 93 controlled by valve 95,and a flux outlet line 91 controlled by a valve 99. The line 91! has itsinlet end extending below the liquid level in container 81 The jacket 9|is adapted to be heated by a heating coil [0| arranged in an electricalcircuit containing a suitable source of current (not shown). A pressureregulator H13 in line 93 facilitates maintenance of uniform fluidpressure in container iii.

In the form of apparatus illustrated in Fig. 4, the fluid-tight jacketedflux container H l is con structed in manner somewhat similar tocontainer H of Fig. 1. An aspirator M5 in the main fuel gas line fill isso arranged that the velocity of the main body of gas flowing throughfuel gas main line l i! aspirates into the said main body a regulatedamount of fuel gas more or less saturated with volatile flux. The fuelgas flows to the flux container l l l through inlet line H9 controlledby valve i2l. The outlet line from aspirator i it, and a valvecontrolled oxygen conduit l22 are respectively connected with a blowpipeT. A valve I25 in the main fuel gas line controls the fiow of fuel gasto the aspirator i it.

When using high pressure liquefied fuel gases such as dissolvedacetylene, the fuel gas may be saturated with the flux in a cylinder,and this flux saturated mixture under the existent pressure may beadmixed with a regulated amount of fuel gas to provide a welding gashaving the desired content of flux.

It will be understood that it is possible to utilize a mixture of fluxesinstead of but one, by introducing such mixture into the flux chamber,or by the use of multiple or plural bypass equipment generally similarto that illustrated.

When desired, the rate of feed of volatilized 2, the various apparatusespecially adapted for flux to a welding gas may be regulated andcontrolled by controlling the rate of vaporization of the flux. This canbe readily done with the apparatus shown in Fig. 3 by disposing theinlet end of line 9'! above the liquid level in vessel 81, closing valve95 and controlling the current passing through the heating coil I0 I Theflux passes out through line 91 into the fuel supply of the torch.

Figurefi illustrates apparatus adapted for use in incorporatingvolatilizable fiuxes into large volumes of gas, such as are required forthe operation of a number of welding or brazing torches on an assemblyline. The flux is vaporized into a regulated bypassed portion of thefuel gas; The amount of material vaporized in the flux container I39 maybe readily controlled by regulating the amount of heat supplied to thesaid chamber, as by an electrical heating coil I32 in an any residualmoisture present, a

electric circuit having therein. a rheostat, variable transformer orother current regulating device I3I, and a source ofv electric current(not shown). Otherwise, the container I3Il and associated parts aregenerally similar to container 15 and corresponding parts shown in mg.2. In

operation, a portion of fuel gas is bypassed from main line I33 throughthe valve-controlled branch line I34, the liquid in container I St, andoutlet line I36 where the bypassed fluid containing flux is mixed withthe main body of fuel gas flowing past a control valve I31 and fed toinlet lines I 38 of a plurality of blowpipes T. A flash-back arrester ortrap 989 preferably is operatively disposed in each of the inlet linesISt. A main oxygen line Itl having branch lines Mil, I60, conductsoxygen to the respective blowpipes.

Figure 6 illustrates one form of apparatus especially adapted for usewith fuel gases which contain substantial amounts of moisture. Anexample of such gas is low pressure generated acetylene which issaturated with moisture at the existing temperature and pressure. Such agas is difiicult to dry and to further process be-' cause of the lowallowable pressure drop through the system. The apparatus showncomprises a fuel gas conduit I having therein a pressure regulator I52.The outlet end of the conduit I50 is connected with a header ISt havinga slotted or perforate portion I extending within the lower portion of adrier vessel I 56 below a foraminous plate or screen member I58 mountedtherein. The vessel I56 has a flanged closure member I60 adapted to bebolted or otherwise secured to the upper flanged margin of the vesselI56 to provide a fluid-tight seal. The vessel I56 preferably is filledwith alternate layers I62, I64, respectively of a desiccating agent suchas solid calcium chloride, and of a supporting material such as rockwool or glass wool. A conduit I66 having therein a valve I68 establishescommunication between the drier I 56 and a flashback arrester'or trapI10. A flexible conduit I12, desirably of aluminum or bronze seamlessflexible tubing, connects the trap outlet with the fuel gas inlet of theblowpipe T. The latter has an oxygen inlet connected with a suitablesource of oxygen under pressure through a conduit I16 having therein apressure regulator I18 and a cut-off. valve I80. A flux vessel I82,having a fluid-tight closure I84 in its top, and having avalve-controlled bottom draw-01f line I86 is adapted to hold a body ofliquid flux I90. If desired, the vessel I82 may be provided with aheating jacket or the equivalent. A conduit I92 having therein a valveI94 connects the interior of vessel I82 with conduit I66 at a pointtherein between the drier I56 and valve I68. The outlet end of conduitI92 is directed to discharge fuel gas laterally of and adjacent thesurface of the flux in vessel I82 near one side thereof. A fluid outletconduit I96 having therein'a valve I98 connects the upper part of vesselI82 at a point remote from the outlet of conduit I92 with conduit I 66between the valve I68 and'the trap I10. For removing from theimpregnated gases any solid components whichat times may be present asthe result of the hydrolysis of flux caused by pressure-tight filterunit is interposed in the conduit I66 between valve I68 and the trapI10.

The filter unit, in the form illustrated in Fig.

6, is composed of an internally-threaded tubular r5; member 202 havingend caps 204, 204, threadedlyinto the body of flux at secured thereto.The respective caps are con nected through apertures therein with theconduit I 66'. A plurality of filter cartridges or pads 29% of hairfelt, or other suitable material are closely packed within the unit andare readily replaceable when necessary in obvious manner.

Other means than that shown in Fig. 6 can be used for dehydrating thegases flowing to the flux-introducing chamber; and/or other means thanthose shown may be employed for removing from the gases flowing to ablowpipe any solid components which would tend to clog the blowpipepassages, or for impregnating with a volatile flux the fuel gas flowingto a heating operation.

In the use of the apparatus shown in Fig. 6, a fuel gas such 'as lowpressure generated acetylene is passed at a selected pressure throughthe drier I 56 where it is dehydrated. The valves I68, I94 and I 98 areso adjusted that a selected portion of the fuel gas flows over thesurface of the liquid flux I90, and this portion of gas containing fluxis returned to the line I66 and then flows through the filter unit andtrap I10 to the blowpipe, to the latter of which oxygen containing gasflows through conduit I16. Any solids precipitated in vessel I82 byhydrolysis of volatile flux may be removed through line I86. The filterunit and trap I10 remove any solid hydrolysis products present inconduit I 66.

the entire body of fuel gas through the flux con tamer, rather than tobypass part of it only, as

such flux is at room tem- In the case of the ,less volatile fluxes, theamount of flux vapori ed'by bubbling fuel gas through it depends, for agiven bubble size, upon the length of time that the latter is in contactwith the flux, up to the-point of saturation. To control this time, thel'fuel gas may be delivered a greater or lesser depth below the surfaceof the flux; or the velocity of the gas may be varied, The size of thebubbles may be varied by obvious means to assist in this control ofvolatilization. Thus, interchangeable tips having orifices of varioussizes may be provided in the gas inlet to the flux container. Porousdiffusers of selected porosities, such as those made of alundum,sintered glass, or porous artificial filter stone, may be used forproducing fine bubble sizes.

When the fluxing liquid is maintained under a definite positivepressure, the liquid may be sprayed in either vapor or liquid form ontothe work being welded at the welding zone, or it may be introduced'intothe fuel gas line and mixed therein with the fuel gas. The rate ofvolatilization of the flux may be controlled by regulating 3g;

the temperature of the mixing chamber. Room temperature is suitablewhen. using such volatile fluxes as trimethyl borate, and the azeotropicmixture of triethyl borate and ethanol. If tripropyl or tributyl borateis used, the mixing chamber should be heated externally.

In utilizing the invention in connection with the apparatus of Fig. 1,fuel gas such as propane, dissolved high pressure acetylene or lowpressure generated acetylene is fed from supply line 35, the valves 38and 49 being so adjusted that the gas flowing over the surface of theliquid flux in container II will entrain a suitable selected amount offlux. This fluid mixture then flows through line 39 to line 40 where itis mixed with sumcient fuel gas to provide a fuel gas mixture having thedesired amount of the flux. This mixture then flows through the filter4| wherein any irt, boric acid particles, etc. are removed from the gas,which then flows to the manifold 53 or toa blowpipe. A uniform level offlux can be maintained in container II by the means described, but thisis not essential as a rule. Where fluxes of relatively low volatilityare used, e. g. tripropyl borate or triethyl borate in ethanol or inisopropanol, the container I I may be heated to facilitatevolatilization of the flux, or the apparatus of Fig. 2 may be used,either unheated or heated. The 100% trimethyl borate flux is especiallysuitable for bronze welding using substantially dry fuel gas such asdissolved high-pressure acetylene. The azeotropic solution of triethylborate in ethanol is quite effective for welding bronze even when thefuel gas contains considerable moisture, as in the case of low or mediumpressure generated acetylene. However, in the latter case considerableboric acid forms in the flux container and must be periodically removed.This can be minimized by partly drying the gas 0. flowing to the fluxcontainer.

The following table presents data illustrative of results secured in thepractice of the invention:

Team: I

A para- Specimen Welding Weldin Item tu s used Flux used welded rod gasg A 100% TMB. 1 M X A do 2 N X A 3 0 X B 1 M Y B 2 O Y B 3 0 Y A 4 O X B4 0 Y Ultimate tensile Item strength Remarks oi wegied 000 Specimenfailed in copper.

Speegnen failed in plate.

0. Failures in copper base metal. Failgi in plate.

Do. Do.

' Apparatus A=Apparatus type illustrated in Fig. 1. IB=Apparatus typeillustrated in Fig. 2.

, Flux 100% TMIB=100% trimethyl borate.

' TEB=35%. solution of triethyl borate in ethanol.

Specimen 1=1"x electrolytic copper strip.

2= thick deoxidized copper plates, bevel,

butt-welded.

3=%" thick yellow brass (-40) plates, 40

bevel, butt-welded.

4=High tensile strength steel plate.

Welding Rod Composition X=high-pressure dissolved acetylene.Y=low-pressure generated acetylene.

The amount of flux introduced into the gas mixture may vary inaccordance with the character and composition of the welding gas, thenature of the metals to be welded or brazed, and the composition of thewelding rod. Amounts of trimethyl borate ranging from 25 to 50 cc. per100 cubic feet of dissolved acetylene have given excellent results inthe brazing of copper and brass, although other amounts of the flux alsomay be utilized effectively.

When adding more than one type of volatile flux, especially in caseswhere the vapor pressures of the several fluxes are different, a dualbypass system has been employed in which part of the fuel gas is passedthrough a chamber containing one volatile flux and another portion ofthe fuel gas is passed through another chamber containing a secondvolatile flux. By means of needle valves the relative gas flows throughthe chambers are controlled, so that the outflowing gases containdesired proportions of the two fluxes. Obviously more than two fluxescap in this manner be introduced concurrently into a fuel gas stream.

It will be obvious from the preceding description that uniformregulation is secured of a volatilizable flux fed to a welding zone, orto a welding gas flowing thereto, irrespective of substantial variationsin the rate of flow of the welding gas. The introduction of flux isregulated in accordance with and in response to the rate of flow of thewelding gases flowing to the welding zone-or to the volume of suchgases-variations in such flow rates producing corresponding variationsin the rate of feed of flux to the said zone. The amount of flux thusfed can readily be regulated by adjusting the partial vapor pressure ofthe volatile flux by thermal or other means, in the presence of aflowing stream'of the welding gas, or by selection of a flux having asuitable vapor pressure at atmospheric temperature and pressure.

The term welding tion and claims to designate not only high temperaturewelding operations, but also brazing and soldering operations as well.The present invention is eminently suitable for use in the welding orbrazing of nickel, copper, brass, bronze, low carbon steel and highchromium ferrous alloys.

This application is a continuation-in-part of our copending application,Serial No. 56,042, filed is utilized in the speciflca- December 24,1935,for improvement in Volatile We claim:

1. In a process for welding metals, the steps which comprise supplyingwelding gases consisting of a fuel gas and a combustion-supporting gasto a blowpipe nozzle to produce a welding flame; introducing into atleast one of said welding gases a volatile flux, and regulating theamount of flux thus introduced by adjusting the partial pressure of thevolatile flux vapors in the presence of the said welding gases.

2. In a process for welding metals, the steps whichcomprise introducingat a uniform regulated rate a selected portion of a welding gas flowingto a welding zone into intimate contact with a body of a volatile fluxhaving a constantly uniform surface level, and maintained underconditions whereby a substantial portion of the flux continuously isvolatilized and mixed with the said welding gas portion, therebyproducing an intimate mixture of the welding gas and flux, andcontinuously introducing the resultant mixture at a uniform rate intothe residual portion of the welding gas flowing to the welding zone.

3. In a process for welding metals, the steps which comprise introducingat a uniform regulated rate at least a portion of a welding gas flowingto a welding zone into intimate contact with a body of a volatile fluxhaving a constantly uniform surface level, and maintained underconditions whereby a substantial portion of the flux continuously isvolatilized, while concurrently applying heat to the said body of flux,thereby producing an intimate mixture of the welding gas and flux, andcontinuously and uniformly introducing the resultant mixture into astream of welding 'gas flowing to the welding zone.

4. In a process for welding metals, the steps which comprise introducingat a uniform regulated rate at least a portion of a welding gas flowingto a welding zone into a body of a volatile flux maintained underconditions whereby a substantial portion of the flux continuously isvolatilized, thereby producing an intimate mixture of the welding gasand flux, continuously introducing the resultant mixture at a uniformrate into intimate contact with a regulated stream of welding gasflowing to the welding zone, thereby producing a diluted fluid mixtureof welding gas and flux, removing solid impurities from the lastnamedmixture, and feeding the residual fluid mixture to the welding zon 5. Ina process for welding metals, the steps which comprise introducing at auniform regulated rate at least a portion of a welding gas flowing to awelding zone into contact with a body of a volatile flux maintainedunder conditions whereby a substantial portion of the flux continuouslyis volatilized, while maintaining the said body of flux under asubstantially constant pressure and elevated temperature during contactof the said welding gas and flux.

6; Process for welding metals which comprises conducting a welding gasinto intimate contact with the surface of a liquid body of avolatilizable flux, thereby impregnating the gas with said flux,regulating the partial pressure of the vapors of said body of flux,thereby controlling the extent of impregnation of the welding gastherewith, and introducing the thus-impregnated gas at a regulated rateinto a flowing stream of a welding gas flowing to a welding zone.

'7. Process for \welding metals which comprises conducting a welding gasinto intimate contact with the surface of a liquid body of avolatilizable welding gas.

flux, thereby impregnating the gas with said fi while regulating thetemperature of the said body of flux, thereby controlling the extent ofimpregnation of the welding gas therewith, and introducing thethus-impregnated gas at a regulated rate into a flowing stream of awelding gas flowing to a welding zone.

8. Process for welding metals which comprises directing a stream ofwelding gas to a welding zone while bypassing a selected portion of thesaid stream at a uniform rate into intimate contact with a surface filmof a volatilizable liquid flux which upon vaporization yields vapors ofsubstantially constant composition, thereby uniformly impregnating saidbypassed portion with vapors of the said flux, and thereafter intimatelymixing the thus-impregnated portion with the main portion of the weldinggas flowing to the Welding zone.

9. Process as defined in claim 8 wherein the volatilizable flux is anazeotropic solution of an alkyl borate in a volatile solvent therefor.

10. Process for welding metals which comprises flowing a stream of amoisture-containing welding gas to a welding zone, removing moisturefrom the said gas, bypassing a selected portion of the resultant gasinto intimate contact with at least one volatile flux, therebyimpregnating the bypassed portion with said flux, regulating the partialpressure of the vapors of said flux with which the welding gas iscontacted, thereby controlling the extent of impregnation of the latterwith said flux, mixing the said bypassed flux-impregnated portion ofwelding gas with the main body thereof, and conducting the resultantmixture to a welding zone.

1. Process as defined in claim 10, wherein the welding gas is anacetylene selected from the group consisting of low-pressure generatedacetylene and medium-pressure generated acetylene.

12. Process as defined in claim 10, wherein said volatile flux is an atleast approximately azeotropic solution of an alkyl borate in an alkylalcohol.

13. Process for welding metals which comprises flowing a stream of amoisture-containing welding gas to a welding zone, removing moisturefrom the said gas, bypassing a selected portion of the substantially drygas into intimate contact with at least one volatile flux selected fromthe group consisting of alkyl borates, alkyl silicates, and solutionsthereof in alkyl alcohols, thereby impregnating the bypassed portionwith said flux, regulating the vapor pressure of the said flux withwhich the bypassed portion of welding gas is'contacted, therebycontrolling the extent of impregnation of the latter with said flux,mixing the resultant flux-impregnated portion with the main body ofwelding gas, and conducting the resultant mixture to a welding zone.

14. Process as defined in claim 13, together with a step of removingfrom the flux-impregnated bypassed portion of welding gas any solidmaterials present therein subsequent to mixing said bypassed portionwith the main body of 15. Process for welding metals utilizing aliquefied welding gas and a volatilizable liquid flux, which comprisessaturating the liquefied welding gas with said liquid flux, convertingsuccessive portions of the resultant mixture to the vapor phase" at aselected rate, and intermixing such portions of the mixed vapors withaifilding gas flowing to a welding zone.

16. In a process for welding metals, the steps amount of flux thusintroduced irrespective of which comprise supplying welding gasesconsistthe total volume of welding gases flowing to the ing of a fuelgas and a combustion-supporting welding flame. gas to a blowpipe nozzleto produce a welding THOMAS H. VAUG-m. flame; introducing into at leastone of said weld- ARTHUR R. LYTLE. ing gases a, volatile flux, andregulating the

